Conventional liquid crystal elements used for watches and electronic calculators mostly make use of displays operated by the twisted-nematic (TN) mode wherein a nematic liquid crystal is arranged in a twisted structure. The response speed in this mode is 20 ms at the most under the present technology. On the other hand, an attempt for a display using a smectic liquid crystal is being made. A liquid crystal having smectic C* phase or smectic H* phase exhibits a ferroelectric characteristic, and such liquid crystal has come to the fore since it was found by Meyer et al. (refer to Journal de Physique, Vol. 36, L69, 1975). Such liquid crystal has a responsiveness of less than 1 ms, as is reported by Clark et al (refer to Applied Physics Letters, Vol. 36, P. 899, 1980), and so it is expected as a liquid crystal which will be able to open up a new field in an application of liquid crystals.
Further, in the ferroelectric liquid crystal element, it is important to arrange molecules of the liquid crystal in parallel and a preferred direction to a substrate, and to provide the element with a memory property.
As conventional methods for orienting the molecules of the ferroelectric liquid crystal uniformly in parallel and in a preferred direction to the substrate are proposed an application of a strong magnetic field and an application of a shearing stress to the liquid crystal, and an orientation by a spacer edge (refer to, for example, Shizen, July, 1983, pp 36-46 and Optronics, September, 1983 pp 64-70). On the other hand, there are a silicon monoxide oblique vacuum evaporation method and an organic polymer film rubbing method which have conventionally been used for a molecule orientation control of nematic liquid crystals and cholesteric liquid crystals. In the case of ferroelectric liquid crystals, however, these methods are not effective for a uniform molecule orientation. Of various organic polymer films, a polymer of imide series presents a relatively uniform orientation. The polymer film of imide series, however, has a problem of not causing the memory property for the element. As for the memory property, a proposal has been made by N. A. Clark and S. T. Lagerwall in Applied Physics Letters, Vol. 36, P. 899, 1980 and U.S. Pat. No. 4,367,924. According to the proposal, however, the memory property cannot be obtained unless the gap between the substrates of the liquid crystal element is reduced to extremely small sizes such as 1 .mu.m, and a practical liquid crystal element is not yet produced. No practical production example of the elements with such a thin liquid crystal layer thickness is reported, even with the TN element which has been put to a practical use, and a possibility of practical production of such elements even from now on is extremely low. This is because the liquid crystal layer is required to be formed with a uniform thickness whose error has to be controlled less than 10% throughout the whole area of the layer, and the thinner the thickness of the layer, the harder the control of the thickness.
At present, therefore, even for a ferroelectric liquid crystal element having a practical cell gap of more than 4 .mu.m between the substrates, an orientation control film which satisfies the requirements of both uniform orientation and the memory property simultaneously has not been found out yet, and so it has been impossible to commercially manufacture ferroelectric liquid crystal elements by the conventional liquid crystal element manufacturing method.
Thus, the present inventors have studied various kinds of polymer films and inorganic films in order to find out the orientation control film which is capable of causing not only uniform molecule orientation but also the memory property for the element.